The present invention relates to a body mounting arrangement for a truck, and more particularly to a body mounting arrangement whereby a bonnet type body is supported on a frame.
It is conventional practice to support a bonnet type body on a frame via a plurality of pairs of mount rubbers between the body and the frame. More specifically, a first pair of mount rubbers are disposed to support the front of the body, a second pair of mount rubbers to support the front portion of the floor of the cabin, and a third pair of mount rubbers to support the rear portion of the floor. There are two types of mount rubbers which are widely used for this purpose. One type may be called as a "compression type mount rubber" which is adapted to be elastically compressed to bear vertical stress occurring when the body moves vertically relative to the frame, and to elastically shear to bear horizontal stress occurring when the body moves horizontally relative to the frame. Besides, the mount rubber of this type show a higher stiffness coefficient upon bearing the vertical stress, and a lower stiffness coefficient upon bearing the horizontal stress. The other type may be called a "shear type mount rubber" which is adapted to elastically shear to bear vertical stress occurring when the body moves horizontally relative to the frame, and to be elastically compressed to bear horizontal stress occurring when the body moves horizontally relative to the frame. Besides, the mount rubber of this type show a smaller stiffness coefficient upon bearing the vertical stress, and a larger stiffness coefficient upon bearing the horizontal stress.
In the case where a body is supported on the frame by mount rubbers of the compression type only, the rear portion of the cabin tends to shake laterally although vertical impact and longitudinal impact that are applied to the frame are damped and transmission of such impacts to the body is reduced to a sufficiently low level, and vibration of the frame is prevented from being transmitted to the body thereby suppressing the noise level within the cabin to a sufficiently low level.
In order to solve the above mentioned problem, it has been proposed in Laying-open Japanese Patent Application No. 59-186783 to use the compression type mount rubbers for supporting the front of the body on the frame, and the shear type mount rubbers for supporting the frame portion and rear portion of the floor of the cabin on the frame.
Applicants are also aware, as a known practice, of using compression type mount rubbers for supporting the front of the body on the frame, shear type mount rubbers for supporting the front portion of the cabin floor, and compression type mount rubbers for supporting the rear portion of the floor.
In the above mentioned conventional body mounting arrangements, since the front of the body and the front portion of the floor of the cabin where first and second pairs of mount rubbers support are displaced to the front of the center of gravity of the cabin, the combined equivalent stiffness coefficient , in the horizontal direction, of the first and second pairs of mount rubbers are equal to or greater than the combined stiffness coefficient of the third pair of mount rubbers supporting the rear portion of the floor of the cabin and displaced to the rear of the center of gravity of the cabin. Thus, the rear portion of the floor of the cabin is subject to lateral shake with a large amplitude. This degrades riding comfort of the occupants in the cabin. This lateral movement of the cabin will become the maximum at resonant frequency ranging from 7 to 12 Hz. If there is non-uniformity in tire and/or imbalance between tires, such lateral shake occurs during vehicle operating speeds from 50 to 90 km/h.
An object of the present invention is to provide an improved body mounting arrangement which is effective in reducing the amplitude of lateral shake which the rear portion of the floor of the cabin is subject to, while effectively alleviating transmission of vertical and longitudinal impacts applied to the chassis to the cabin and the transmission of vibrations of the frame to the cabin.